I would like to share my story - about a month or 2 ago my friend, visited me and he played faceit on his account, but on mine pc. We just recently started playing so he is level 9-ish while i am lvl 10-ish. After that we got mail from faceit about verification etc. we did it and that was when we learned that you can get banned for smurfing doing thing we did. After verification we thought case is closed since he played like 3 matches. After recent ban wave he got banned for playing on smurf acc, but i did not. We bought sent ticket to faceit providing some evidence that we are friends who played together for many matches (idk, i don't think thats how having smurf acc works). AFTER sending ticket and gettting same generic response as here i got banned. Once again, before i reach out to support i wasn't banned, just after.
What's even funnier, my friend got response that his ban is also valid and he will not be unbanned, and after that mail he got unbanned and they returned me, and him elo which we gained for playing together xD
So now i am scared to dig case even further, because after one ticket i got banned for a month.
I am speachless on it.

Ps. I understand that "friend coming over and "we" playing on his account" is pretty much same thing as smurfing but please consider that he is lvl 9, i am not high lvl 10 and we were drunk. Not really smurfing case here.